Note: Descriptions are shown in the official language in which they were submitted.
, ~WO 93~2432~) PCI /US92/04473 -
2136~15 ~
TITLE
AN IMPACr-RESISTING GLAZING STRUCI URE
_LD~2E~E I~VENTIOy
This invention relates to glazing structures which sllbstantially -
resist penetration by objects propelled by humans or other means. In ;
particular the structures resist penetration by storm driven objects and
objects, commonly used in burglaries to gain entry, such as bricks, rocks,
sticks, baseball bats, and tire irons.
BACKGROIIND OF THE INVENTIO~
Various types of glazing structures have been developed which
resist penetration by objects which are propelled against a surface of the
structure. Glass larninations, commonly referred to as safety glass, consisting
of a plurality of glass sheets and interlayers have been made. These
structures are generally thick. heavy constructions which are not adaptable
for use in usual framing apF ltions and are expensive to fabricate. In
addition, plastic sheeting, such as polycàr~onate sheeting has been used.
However, such sheeting is relatively costly and has lirnited chernical and
2 o weathering resistance. Other glass/plastic larninates are known, including ~ `
insulated glazing structures. These structures suffer from the sarne
deficiencies as noted above. Also, the insulated structures tend to fog due to
condensation of moisture which enters the gas space between the glass panes.
What is needed is a light weight impact resisting structure which is adaptable
2 5 for use in usual framing applications which avoids the problems noted.
.
SUMMARY OF THE INVENTION
This invention provides a glazing structure which is inexpensive
to manufacture and provides excellent impact resistance. In its simplest form
3 o the structure consists of a c ~ort frame and a glass/plastic laminate secured
in the support frame. Th~ inate is comprised of a sheet of glass, a
specially oriented polyester film and a sheet of adhesive such as polyvinyl
butyral fiilm sandwiched there between. The laminate is adhesively sealed in
the support frame. In an insulating glæing embodiment the glass/plastic
3 5 laminate is combined with a sheet of plain glass with the plastic sheet being
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on the inside of the structure. When installed, the glass/plastic side should
face the direction from which an impact is expected. The interior plain glass
does not provide impact res`i~t`~nce. It is indeed surprising that the relatively
thin glass/plastic structure will withstand the onslaught of projectiles
5 retaining security against the elements, wind and rain, as well as attacks hy
vandals.
BRIEF DESCRIPTION OF THE DRAWINGS -~
FIG. 1 is a schematic section, show~ng the structure of one -
embodiment of the glass/plastic laminate of the invention. ~-
FIG.2 and FIG. 2A are schematic sections showing insulated
glazing embodiments of the invention.
FIGS. 3-9 show graphic depictions of properties of a polyester
film useful in the invention.
DETAILED DESCRIPIION OF THE I~VENTION
Referring to FIG. 1 of the drawings, an impact resistant glazing
structure is comprised of support frame 12 and a multilayered laminate
comprised of a sheet of glass 14, polyester film 16 which will be described
with more particularity later herein and a sheet of adhesive film 18 which is
2 o sandwiched between the glass and polyester film. The larrunate is secured in frame 12 by an adhesive sealant 20.
Glass sheet 14 is positioned in a direction likely to receive an
impact. Surprisingly, the thickness of the glass does not materially influence
the impact resistant character of the structure. The glass may be tempered or
2 5 untempered. Tempered glass is preferred for some applications.
Thicknesses of the glass may vary from 2 rnm to 12 rnm, the major
consideration being to keep the thickness to a dimension which can be
accommodated in a standard glazing frame.
In another embodiment shown in FIG. 2, arl insulated glazing
3 o structure is provided by sealing in a frame 30 two glass sheets 32 and 34.
Sealant 31 assists in secur~ng the glass in fr~ne 30. Polyester film 36 is
laminated to glass sheet 32 using adhesive film 38. A gas space 40 about 5/8
in (15.875 mm) wide separates the two sheets of glass. An alurninum spacer
42 contair~ing a dessicant 44 separates the glass sheets. A sealant 46 provides
3 5 a moisture barrier around the glass sheets. There are small holes in the
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3 ~-
spacer leading into gas space 40. These holes allow moisture which is sealed
inside the unit during its rnanufacture to become absorbed by the dessicant,
trapping it so that it does not condense and fog the glass. Sealing member
48 extends around the periphery of the structure providing an air-tight seal
s for the space between the sheets of glass. Slight imperfections or rupture of
sealing member 48 tend to perrnit wicking of moisture in to gas space 40.
In a preferred embodiment of this invention shown in FIG. 2A,
an insulated glazing composite comprising two glass sheets 52 and 54 are
secured in support frame 50. The glass sheets are spaced apart and she~t 54
0 has on its interior surface a polyester film 5~ adhered to the interior surface
of the glass by a sheet of adhesive film 58. An aluminum spacer 60
containing a dessicant 62 separates the glass sheets. A sealant 64 provides a
moisture barrier around the glass sheets. There are small holes in the spacer
leading into gas space 66. These holes allow moisture which is sealed inside
15 the unit during its manufacture to become absorbed by the dessicant,
trapping it so that it does not condense and fog the glass. The glazing
structure has a sealing member 68 around its periphery to mairltain an air~
tight space between the sheets of glass. The polyester film SS and adhesive
sheet S8 approach but do not contact the sealing member. The insulated
2 o structure is sealed in frame 50 using a sealant 51. Quite surprisingly, spacing
the polyester film 56 and adhesive sheet 58 from the sealing member 68 and
spacer 60 does not significantly affect the impact resistance of the structure.
It is also surprisirlg that this embodiment alleviates the problem of moisture
being wicked into the air-tight space 66 between the s~eets of glass.
2 s Although it is usual to place a dessicant in the space between the sheets ofglass, with the influx of moisture the dessicant soon becomes moisture laden
and ineffective.
The polyvinyl butyral adhesive sheeting may be selected from
the many commercially a~ailable grades of plasticized polyvinyl butyral. A
3 o particularly desirable product of the type disclosed in Moynihan,
US Patent 4,292,372 is sold by E. I. du Pont de Nemours & Co. under the
trademark Butacite'~9. The polyvinyl butyral film should have a thickness
from 10'to 60 mils (0.25 rnm to 1.52 mm). Other adhesive sheeting materials
such as polyurethanes and the like may be substituted for the polyvinyl
3 5 but~rral film.
.
WO 93/24320 PCl/VS92/04473
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Polyester film which is asyrnmetrically oriented is generally
descri~ed in Knox, US Patent 4,072,77~,~however, Knox provides no teaching
of the special requirements for the~dlyester film useful in this invention. .
The polyester film useful in this~ention is asyrnmetrically oriented
preferentially in the transverse direction (TD) and heat set. In-plane
orientations of crystallites and arnorphous molecules and attendant
properties provided thereby are very important for impact resistance of the
glass laminates of this invention. Transverse direction (TD) and machine
direction (MD) as used herein refer to the direction of travel of the polyester
web during its manufacture. The polyester film should have a thickness from
4 to 14 rnils (0.10 rnm to 0.36 rnm). The outer surface of the polyester film
may be coated with an abrasion resistant material as disclosed in Knox.
The polyester film useful in this invention should have a
special in-plane distribution of crystalline and amorphous phases. All (100)
planes of the polyester crystals should lie in the film plane and crystals with
molecular or chain axes are oriented toward the TD. In addition molecules
in the amorphous region are oriented preferentially in the TD. The overall
orientation of both the crystalline and amorphous phases as measured by
refractive index is higher along the TD. Distribution of the orientation of the
2 o crystalline and amorphous orientations can vary, as measured by refractive
index, fluorescence spectroscopy and wide angle x-ray pole figure analysis, by
up to 20% of the values shown in FIGS. 3-11 and still provide a film which
when incorporated in the laminated structure of this invention gives excellent
impact resistance.
2 5 FIGS. 3 and 4 show crystalline orientation for polyethylene
terephthalate films useful in this invention. Referring to FIG. 3, wide angle
x-ray pole figure analysis of a polyethylene terephthalate film from ( 105
planes shows an absence of any intensity in the center of the pole figure
which indicates an absence of machine direction ~MD) oriented crystals in
3 o the film. It shows that crystals with molecular chain axes are oriented toward
the TD. At a particular TD draw ratio properties along the MD and TD
become the same in the film plane. This is defined as '~alanced properties"
and the particular TD draw ratio as the "balance point". The film is
preferentially, i.e., "over-oriented", along the TD after achieving the
3 5 '~alanced point."
-`' w0 93~24320 2 1 3 6 ~ 1 5 Pcr/uss2/o4473
The film is highly uniplanar. This is determined from the
benzene ring orientation which lies in the (100) planes. As shown in FIG. 4,
the angle (phi) describing the intensity arising from the (100) planes is about
15
FIG. S is a polar plot showing the amorphous orientation of
molecules in the amorphous phase of the film as determined from the chain
intrinsic fluorescence spectroscopy at 390 nm. The distribution of intensity
arising from the intrinsic fluorescence shows that the amorphous orientation
at different angles in the filrn plane is larger along the TD. As shown in FIG.
6 the overall molecular orientation (in crystalline and amorphous planes) is
also dorninant along the TD.
FIGS. 7-9 are polar plots showing the distribution of
mechanical properties such as tensile modulus, tensile strength and F-5
(stress at 5~o strain in the stress-strain curve) at different angles in the film
plane due to the different molecular orientation described above. In all
cases the mechanical properties are dorninant along the TD.
The polyester film may be prepared by extruding molten
polymer onto a cool quench roll to form an amorphous film using the method
and apparatus described in U.S. Patent No. 3,223,757. The amorphous filrn
2 o is stretched at an elevated temperature first in the MD, and it is then
stretched a greater amount in the TD. Stretching may be carried cut
simultaneously is the TD and MD so long as the film is preferentially
asymmetrically oriented to provide dornillant physical properties in the TD.
The present invention has been described and exemplified with
2 5 particular reference to the use of polyethylene terephthalate film, however, it
is to be understood that the invention comprehends using any similar
preferentially asymmetrically oriented polyester films, copolyesters such as
copolyrners of polyethylene terephthalate and polyethylene isophthalate, as
well as other polyesters such as polyethylene naphthalate. In addition the
3 o polyester film may be coated, for example with a reflective coating for solar
heat control, and the film can be tinted and/or printed for aesthetic and/or
commercial advertising purposes.
In preparing the glæing structures of this invention the
polyester f;~m is bonded to the glass using an adhesive such as polyvinyl
3 5 butyral by applying heat and pressure to the structure. An abrasion resistant
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material may be applied to the polyester outer surface and the combined
structure cured at temperatures fr~rn about 130 to 150 C. for 7 to 180
rninutes. The resulting bonded~structure is optically clear. Insulated glazing
stn~ctures may be prepared using the glass/plastic laminate of this invention
assembled using known components by known methods.
Care must be taken to securely anchor the glazing in the
fr~ming member which may be selected from known materials such as wood,
plastics such as polyvinyl chloride, aluminum and steel. It has been found
that an overlap of from about 3/8 to 3/4 in.(0.95 to 1.9 mrn) at each edge of
the glazing is needed to retain the glass lam~nate securely in the frame. The
- glazing is sealed in the frame using known sealants such as room temperature ~ -
vulcanizing (RTV) silicon sealants and the like.
The invention will be further illustrated by the following
examples.
EXAMPLES
EXAMPLE 1 `~
A series of 12 sq ft (1.1 sq m) windows 3 ft x4 ft.(0.9 X 1.2 m)
using wood frarning were constructed using as glazing the following
materials:
(1) 5 mm thick annealed glass, ~ `
(2) 5 mm thick tempered glass,
(3) 5 mm thick annealed glass surfaced with sommercial
polyethylene terephthalate film (PET) 3 mils (0.0762 mm)
thick using a pressure sensitive acrylic adhesive (PSA) to
2 5 adhere the filrn to the glass,
(4) 2 plies of 5 mm thick annealed glass laminated together with a
30 mil (0.76 rnm) polyvinylbutyral film (PVB) interlayer (a
typical safety glass construction), and
(5) 5 rnm thick annealed glass with a laminated plastic composite
3 o of 30 rnils (0.76 mrn) of polyvinyl butryal ilm and 7 rnils (0.178
rnrn) of polyethylene terephthalate film.
The PET film was prepared by stretching an amorphous film in the MD 3.4X
at a ternperature of 9~95C and in the TD 3.8X at temperature of 105-110C.
The stretched film was heat set at 200-205C and heat relaxed under reduced
3 5 tension to give a MD shrinkage of about 0.8~o at 150C.
`; wo 93~24320 2~1l J~ 6 ~ 1~ PCI /US92/04473
The series of structures were subjected to a test which
consisted of simulating 100 mph wind velocity, by pulling a vacuum behind
the window, and then ~itching five standard baseballs weighing 0.32
lb.(145.15 gms) at the window at 85 mph using a commercially available
5 baseball pitching machine. The test was designed to be reproducible and
severe and could represent objects that are either propelled by vandals or by
a wind storm.
Care was taken to adequately secure the glazing in the framing
members. Frames were designed so that at least 3/4 in. t19 mm) of each
0 edge of the glazing was covered by the framing members, and the glazing was
secured in the framing members using RTV silicon sealant.
The results obtained are surnrnarized in Table 1 which follows:
Table 1 -
Sample Results
No. of baseball hits necessary to penetrate
the glass/pla_ticlarninate
(1) Annealed glass Massive failure 1st hit*
(2) Tempered glass Massive failure 2nd hit*
2 o (3) Annealed glass protected with Failure-Penetrated 1st hit*
PET 3 mils (0.0762 mrn) adhered
with acrylic adhesive
(4) Laminated safety glass Failure-Penetrated 5th hit*
(S) Glass laminated with PET/PVB No penetration from all S hits
2 5 plastic composite
(*Vacuum was lost after the window was penetrated.) ~ `~
The only window which would have prevented entry of water or wind after
the test was No. (5), the glazing structure of this invention. In all tests the
3 o glass was cracked.
EXAMPLE 2
A series of tests was conducted to illustrate the penetration
resistance of glazing structures against onslaughts ~pically encounter in
3 5 "smash and grab" burglaries.
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Twelve square foot (1.12 sq m) windows of the type described
in Example 1 were assembled using
(1) Smrn thick annealed glass,
(2) Smm thick tempered glass, and
(3) 5mm thick annealed glass with a larninated piaslic composite
consisting of 30 mils (0.76 mm) of PVB and 7 mils (0.178 mm)
PET ~ilm described in Example 1.
A man weighing 200 lbs. (90.72 kg) then tested the pene~ration
resistance of the windows by attacking thern with a 3 ft (0.9 m) long piece of
0 2 ftx4 ft (0.6 m x 1.22 m) lumber. In the case of both the annealed and
tempered glass, massive failure occurred within seconds of the attack. In the
case of the glass/plastic composite of this invention, the window was battered
until the attacker ran out of energy. Although small holes approximately
1 in x 2 inches (25.4 mm x 50.8 mm) were punched through the glass/'plastic
composite, no hole was large enough to permit extending a hand or arm
through the opening.
